1. Field of the Invention
This invention relates to an inflatable lining for footwear, particularly to an inflatable inner sole with protective and comfortable coatings and surrounds and method for its manufacture.
2. Brief Statement of the Prior Art
Inner soles have been provided for shoes and boots which are formed of a compressible, elastic material such as cellular plastic foams, foam rubber, etc. These inner soles have provided only limited shock absorbency, resulting in little no significant improvement in wearer comfort.
Some prior investigators have provided inner soles with inflated cushions at either the toe and heel areas, and some have provide cushions at both areas with circulation between the two cushions. The cushions have been provided with mechanisms to circulate air and ventilate the shoe or boot during walking activities. Examples of these are: U.K. Patents 2,189,679 and 357,391; U.S. Pat. Nos. 3,180,039, 2,716,293, 1,213,941 and German Patent 3,144,207.
Sport socks are also available for hikers and runners which have a double layer of fabric on the undersurface of the sock in an attempt to prevent blisters.
In some foot apparel, notably in ski boots, an outer shell is molded from plastic and is lined with an inner shoe. Adjustment has been made to the tightness of the outer shell and air bags have been provided across the instep region of the shoe, and elsewhere, and have been provided with an air pump to pressure the air bags, thus forcing the foot against the sole and creating a snugness of the fit of the ski boot. U.S. Pat. No. 4,730,403 and German Patent 2,321,817 are representative of these ski boots.
A water-filled inner sole for shoes has recently been marketed under the trade name “Walk On Water”. While this is an attempt to increase wearer comfort, water is heavy, non-compressible and the inner sole cannot be adjusted for firmness, and cannot provide shock absorbency. Additionally, water is unsuited for use in freezing climates. Also, a leak will wet the inside of the bootwear, and this inner is not breathable.
Another recently marketed innovation is that disclosed in U.S. Pat. Nos. 4,183,156; 4,340,626 and 4,817,304 in which an inflatable inner sole or sole insert is permanently inflated with halogenated hydrocarbon gases. Since it is impossible to preclude diffusion of gases through the plastic, the inflatable insert or inner sole is acknowledged to experience a rapid increase in pressure shortly after manufacture, followed by a slowly declining pressure, thus failing to provide a stable condition. The pressure of the inflatable member also cannot be adjusted by the wearer for varying conditions of use and comfort.
None of the aforementioned prior devices provides a simple, inexpensive solution to comfortable wear and walking in a shoe or boot. The foam inner soles have only a limited value and limited shock absorbency. The remainder of the prior devices, including the pressurization system for ski boots are relatively complex and costly and are often too bulky and cumbersome. Consequently, these devices are not readily acceptable for everyday activities.
In my prior patent (U.S. Pat. No. 5,846,063) I disclose and claim inflatable linings with an on board inflation pump and relief valve which is readily adaptable to mass manufacturing techniques. A preferred application of the inflatable enclosure is that of an inflatable inner sole of footwear.